The present invention relates to a pneumatic coupling for connecting a driven machine member, such as a gantry type carriage of a measuring machine, to a drive member whereby the driven member is moved linearly along a given axis.
For precision applications, such as measuring machines, driven members are connected by pneumatic couplings to the drive members for moving the former linearly along a given axis. Such couplings comprise a bracket integral with the driven member and defining two facing walls perpendicular to the axis along which the driven member travels; and a drive element integral with the drive member, located between said walls, and cooperating with the same via the interposition of a fluid passage.
Movement of the drive element along said axis is thus transmitted to the bracket and, consequently, to the driven member, via the fluid passage, which presents a high degree of rigidity perpendicular to its thickness. Any "spurious" movement perpendicular to the axis of motion, due to vibration or dimensional inaccuracy of the drive system, is prevented from being transmitted to the bracket by virtue of the fluid passage providing for very little friction between the drive element and bracket.
Known couplings of the type briefly described above present several drawbacks, which it is an object of the present invention to eliminate.
Firstly, due to the very small thickness (roughly 10 .mu.m) and the rigidity of the fluid passage, known couplings do not provide for compensating for any spurious rotation about an axis perpendicular to the axis of motion, which rotation is transmitted to the driven members of the machine, thus impairing measuring precision.